Dissertation
Stöorungstheoretische Behandlung der
Strahlungstransportgleichung in dreidimensionalen, bewegten Medien und
Anwendung auf Akkretionsscheiben
(Perturbation approach for the radiative transfer equation
for 3D moving media and application to accretion disks)
Nikolai Kryzhevoi
Abstract:
The multidimensional radiative transfer equation is solved by means of a
perturbation approach in which the full solution is represented by a sequence of
1D solutions. Since the solutions of the higher perturbation orders are given
explicitly, and the methods used for the solution of the zero order equation are
largely analytical, the corresponding code is more efficient than general
multidimensional radiative transfer codes. To examine this iterative procedure
the radiation field of a geometrically thin slowly rotating accretion disk is
calculated. The method is the improvement of those methods which treat the
accretion disk as a system of independent rings because the interaction of the
rings is taken into account in the higher perturbation orders. The influences
of radial gradients, velocity field etc. on the line profile are discussed.
Furthermore, under assumption of the two-stream approximation the analytical
solution of the plane-parallel radiative transfer equation is found for a large
variety of the internal distribution of the de-excitation coefficient
epsilon. A new method for the solution of the equation with the
stochastic epsilon is proposed. In addition, an improved separable
approximation method enable us to obtain fast and accurate solution of the basic
plane-parallel radiative transfer equation without angle and space
discretization.
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